Agricultural vehicles as, for example, tractors employ extremely large tires as is well known. Because of the size of the tires, when servicing of the same is required, they are serviced on site since they cannot be easily transported to a remote servicing site.
Such on-site servicing is frequently accomplished with the use of a tire servicing vehicle such as a truck specially outfitted for tire servicing operations at remote locations.
In the usual case, the truck will be provided with a compressor, frequently mounted under the hood, to be driven by a selectively operated clutch by the vehicle engine. A compressed air tank will also be carried by the vehicle and is operatively associated with the compressor so as to provide a large volume source for compressed air that may be needed during the servicing operation.
It is very common to place a substantial volume of a liquid, typically a calcium chloride solution, in the tires of agricultural vehicles such as tractors. This volume of liquid adds considerably to the weight of the vehicle thereby improving its traction as such a vehicle moves through fields pulling implements or the like. In a tire servicing operation, it is necessary that such liquid be removed from the tire before servicing can be performed. Because the liquid frequently is of a large volume, and even more frequently will be a water based solution of some salt to prevent the same from freezing, it is desirable to save the solution for reuse by replacement within the tire after the same has been serviced.
Thus, conventional servicing trucks are provided with relatively large tanks for receiving the liquid and holding the same during the course of a servicing operation so that it may be subsequently replaced in the tire.
In order to remove the liquid from a tire, probes that may be placed in fluid communication with the interior of the tire via a valve stem or the like are used to interconnect the tire and the tank. A vacuum is drawn on the system to withdraw the liquid. In conventional servicing trucks, a vacuum for the purpose is obtained from the intake manifold of the spark ignition engine used to propel the servicing truck. This method, while working relatively well for its intended purpose, has a sizable drawback for as the system ages, sticky valves or other difficulties may result in the solution within the tire being actually drawn into the intake manifold of the engine and into the combustion chambers themselves. Such can cause severe corrosion and render the engine useless.
Moreover, this method cannot be employed in tire servicing trucks that are powered by diesel engines by reason of insufficient vacuum being present at the intake manifold.
The present invention is directed to overcoming one or more of the above problems.